Machine tool

ABSTRACT

A machine tool, e.g., an extruder or a push bench, for processing a long work-piece, which machine tool comprises a pair of holder members, each including a center pin for holding either longitudinal end of said long work-piece by engaging one of center holes prebored on opposite edge surfaces of the workpiece, a die capable of shaping said work-piece, and a hydraulic piston-cylinder device for moving said die while causing the die to operatively engage the work-piece. The hydraulic pistoncylinder device includes a driving portion for actuating the die and a compensating portion for selectively releasing the stress in the work-piece during the working by the die.

iJnited States Patent ()gasawara 51 June 27, 1972 [s41 MACHINE rooL [72]Inventor: Sadanorl Ogasnwarat Nakashim-gun,

Japan Aikoku Kogyo Kabushlkl Keisha, Nakashima-gun, Aichi, Pref., Japan22 Filed: Dec. 23, 1910- 211 Appl.No.: 100,947

I73] Assignee:

[30] Foreign Application Priority Data Dec. 24, 1969 Japan ..44/l386Nov. 14, 1970 Japan... ..45/l0062l 52 use: ..72/285, 72/297 511 ..B2lc3/12 581 FieldofSearch ..72/274, 285,297, 398, 377,

v [56] References (Iited UNITED STATES PATENTS 3,195,331 7/1965 Curtiset a1. ..72/285 3,290,916 12/1966 Louisetal... ..72/285 345,816 7/1886Tilghman ..72/297 Primary Examiner-Charles W. Lanham AssistantExaminer-Michael J. Keenan Attorney-Waters, Roditi, Schwartz 8; Nissen[57] ABSTRACT A machine tool, e.g., an extruder or a push bench, for

processing a long work-piece, which machine tool comprises a pair ofholder members, each including a center pin for bolding eitherlongitudinal end of said long work-piece by engaging one of center holesprebored on opposite edge surfaces of the work-piece, a die capable ofshaping said work-piece, and a hydraulic piston-cylinder device formoving said die while causing the die to operatively engage thework-piece. The hydraulic piston-cylinder device includes a drivingportion for actuating the die and a compensating portion for selectivelyreleasing the stress in the work-piece during the working by the die.

4 Claims, 14 Drawing Figures P'A'TENTEDJURU I972 3. 672.200

SHEET 2 OF 9 FIGZ FIG.3

PATENIEnJun 27 I972 SHEET 4 BF 9 PIC-3.5

FIG.6

PATENIEnJuuz'r r912 3.672.200

SHEET 6 0F 9 FIG.8

PATENTEDJum m2 3, 672.200 sum 70F 9 FIG.9

PATENTEnJum m2 3. 672,2(30 sum 9 or 9 FIG.I|

@X i HQ I MACHINE TOOL The invention relates to a machine tool forworking an extendedly long work-pieces such as a steel bar into asplined shaft, fluted rod, axially thick pinion or gear and the like bymeans of a die to be axially moved relative to said long workpiece, andmore particularlyto an extruding machine or push bench comprising twoholder members respectively having its center pin for holding said longwork-piece engaged with each center hole previously formed in theopposite ends of said work-piece and a die adapted-to be forcedly movedalong on said work-piece by means of a hydraulic piston-cylinder deviceso as to work said work-piece in said products.

A conventional process of shaping or extruding long workpieces, such assplined shafts, fluted rods, axially thick pinion and the like, has ashortcoming in that the work-piece or the semi-finished product which isto be machined tends t'o-bend during the machining process.

It is well known that, although the art of cold forging process hasrecently been studied extensively for the sake of rationalizing orsimplifying machining process and improving the accuracy of theproducts, the cold forging process has not been used in actualindustrial production due to the bending of the work-piece during theprocess.

. Causes of such bending of the work-piece are considered to be 'in thedifference of the angles of the longitudinally opposing edge surfaces ofthe long work-piece, uneven distribution of flat portions in thework-piece and uneven distribution of hardness in the material of thework-piece. The inventors have found that such bending of the work-piececan completely be eliminated, by suitably controlling the holdingpressure applied to the center holes bored at the longitudinallyopposite ends of the work-piece. Such control of the holding pressure,however, has been impossible with conventional machine tools, becauseeach work-piece is held by stationary holders at the longitudinallyopposite ends thereof despite that the workpiece itself tends toelongate due to the working force applied by the machining tool.

Therefore, an object of the present invention is to obviate theaforesaid difficulties of the conventional machine tools for machining along work-piece, by providing an improved machine tool, wherebyincreasing the accuracy of the products and simplifying the machiningprocess. With the machine tool. according to the present invention, thebending of the work-piece is prevented by. holding the work-piece with aconstant holding pressure, regardless of the elongation of thework-piece during the machining operation, which holding pressure isapplied to the longitudinally opposite ends of the work-piece atprebored center holes by a suitable hydraulic piston-cylinder device.Furthermore, according to the present invention, a die for the machiningoperation may be moved relative to the work-piece, in the so-calledfloating fashion, so as to ensure accurate machining even when thework-piece is slightly bent.

Other objects and advantages of the present invention may be appreciatedby referring to the following description, taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is partly sectioned schematic plan view of a machine toolembodying the presentinvention;

FlG.l-A.is a lateral view of a die to be used in the machine tool ofFIG. 1;

F102 is a partly sectioned schematic view, illustrating the operativeconditions of the machine tool of F IG. 1 at the end of machining awork-piece;

FIG.3 is a partly sectioned partial schematic view, illustrating themanner in'which a finished work-piece is removed from the machine tool;

FIG.4 is a partly sectioned schematic, plan view of another machinetool, according to the present invention;

FlGS.5 and 6 are sectional views, taken along the lines 11 ii and Illll! of FlG.4 respectively;

FIG.7 is a partly sectioned schematic view of the machine tool of FIGA,shown as ready for machining with the workpiece mounted thereon;

FlG.7-A is an end view of a die to be used in the machine tool of H61;

FIG. 8 is a partly. sectioned plan 'view of the machine tool of FIG.7,showing the manner in whichthe right-hand part of the workpiece ismachined;

FIG. 9 is a schematic view similar to no.8, illustrating the work 12including a die holder or left-hand end member of the reciprocatingframework 13 and a flange or a right-hand end member of said frame-work.which are secured to connector rods or beams for connecting said two endmembers of said machine frame 15 and 16 by, suitable joints l7, l7", l8and 18', e.g., nuts, with a spacing therebetween. Theconnector rods 15and 16 of the reciprocating frame-work 12' are slidably held by guidebearings 19 and 20 integrally formed on a righthand upright support wallor support member 11 secured to the machine frame 11. The diameter ofthe rods 15 and 16 is slightly smaller than the inner diameter 'of theguide bearings 19 and 20, so as to allow smooth reciprocation of theframework 12 while causing a die 28 carriedby the die holder 13 of theframe-work 12 to operatively engage a work-piece 46 for machining.

A left-hand upright support wall or support member ll" is secured to themachine frame 11 in parallel with the righthand support wall 11', and apair of guide rods 21 and 22 extending toward the right-hand wall 11'are fastened to the lefthand support wall 11" by suitable joints 23 and24, e.g., nuts, with a spacing therebetween. The guide rods 21 22' actto guide the movement of a center holder 29 holding the neck portion 31of a movable holder member 30. The outer diameter of the neck portion 31is smaller than the minimum diameter :1 of the die 28, such as a splinedie shown in FlGJ-A. The movable holder member 30 holds one end of thework-piece 46 with substantially constant pressure by moving togetherwith the holder member 29, as will be described hereinafter. A fixedholder member 29 secured to the right-hand support wall 11' holds theopposite end of the work-piece 46, so as to cooperate with the movableholder member 30 in holding the work-piece 46 at its opposite edge.

As shown in FlGJ-A, the die 28 carried by the die holder 13 of thereciprocating frame-work 12 has tooth forms 28' for shaping thework-piece 46 into desired shape, for instance, into a splined shaft,axially thick gear, fluted rod and the like.

Each work-piece 46 to be machined by the die 28 in the machine tool ofthe present invention is provided with center holes formed at thelongitudinally opposing edge surfaces thereof. When the die 28, as shownin FlG.l-A, is used, the work-piece 46 is prepared in a cylindrical formwith an outer diameter substantially equivalent to or slightlysmallerthan the maximum inner diameter D of the die 28 as shown inFlG.l-A.

An auxiliary ram cylinder 32, is secured to the left-hand support wall 11" on its opposite surface to the right-hand support wall 11. A piston33 is operatively disp ed in the cylinder 32, and the center holder 29is connected to the piston 33 through a piston rod 34. A stopper 35 maybe provided at the junction between the piston rod 34 and the centerholder 29. Thus, the movable holder member 3.0 carried by the centerholder 29 reciprocates in response to the movement of the piston 33 inthe cylinder 32.

through a checking constant-pressure valve or check valve 36. The valve36 acts to keep the inside operating pressure of the cylinder 32 at aconstant level. A vent hole 39 is provided to expose the joint of thepiston 33 and the piston rod 34 to the atmospheric pressure.

The cylinder 40 for a main ram is mounted on the righthand support wall11 on its surface opposite to the left-hand wall 11". A piston 41 in thecylinder 40 is connected to one end of a piston rod 42, and the oppositeend of the rod 42 is secured to the flange 14 of the reciprocatingframe-work 12 by a suitable joint 43, such as double nuts. Thus, thereciprocating frame-work 12 travels back and forth in response to themovement of the piston 41, which is driven in the cylinder 40 by thehydraulic pressure, so that the die 28 is operatively actuated by thehydraulic pressure acting on the piston 41. The piston 41 defines twopressure chambers in the cylinder 40, each having a fluid passage 44 or45 for receiving pressure liquid, as shown in FlG.l.

The axes of the main and auxiliary hydraulic jacks, or the axes of thepiston rods 34 and 42, are aligned with each other, and the movableholder member and the fixed holder member 27 are aligned with the axesof the two pistons 34 and 42.

in operation of the machine tool of the aforesaid construction,according to the present invention, the work-piece 46 having centerholes preformed at the opposite end surfaces thereof is mounted on themachine tool by engaging one end to the fixed holder member 27 and thendelivering pressure fluid into the piston 32 through the passage 38 andthe checking constant-pressure valve 36 for shifting the movable holdermember 30 toward the fixed holder member 27 through the piston 33,piston rod 34, and the center holder 29, until the movable holder member30 operatively engages the center hole bored at the opposite end of thework-piece 4,6. FlG.l illustrates the work-piece 46 thus mounted. Aspointed out in the foregoing, in the ease of splining by the die;.:1fFlG.l-A, the outer diameter of the work-piece 46 is made" equivalent toor slightly smaller than the maximum inner diameter D of the die 28,before being mounted on the machine tool.

in F162, as the pressure liquid is delivered to the left-hand sidechamber of the cylinder through the passage 44, the reciprocatingframe-work 12 moves rightwards, together with the die 28 securedthereto. Thus, the die 28 operatively engages the work-piece 46 in theso-called floating fashion, so as to form spline grooves 46 on thework-piece 46 by extrusion.

It should be noted here that as the die 28 travels toward the fixedholder member 27 while extruding spline grooves 46', the splined portionof the work-piece 46 tends to expand or elongate in its longitudinaldirection. This elongation acts to compress the fluid in the cylinder 32to the left of the. piston 33, because the right-hand end of thework-piece 46 is held steadfastly by the fixed holder member 27. As aresult, the pressure in the cylinder 32 tends to rise. The constructionof the checking constant-pressure valve 36 is such that as the fluidpressure within the cylinder 32 increases on the left-hand side of thepiston 33, the valve 36 releases the fluid to the outside of thecylinder 32 while allowing the piston 33 to move leftwards, as seen inFlG.2, so as to keep the fluid pressure acting on the piston 33constant. Such movement of the piston 33 can be seen by comparing thepiston positions in FIGSJ and 2. Consequently, the work-piece 46 isallowed to elongate as it is extruded by the die 28, so that it can beaccurately extruded. The inventors have confirmed that extrusions otherthan the illustrated splining extrusion can also be accomplishedaccurately by the machining tool of the invention. Furthermore, thework-piece 46 is held by constant pressure by the movable and fixedholder members throughout the entire machining operation.

Although the sum of the constant pressure from the piston 33 through themovable holder member 30 and the machining pressure from the die 28seems to act on the fixed holder member 27, the actual load acting onthe fixed holder member 27 does not exceed a reasonable limit partly dueto the difference of the lateral sectional areas between the extrudedportion and non-extruded portion 46" of the work-piece 46.

Referring to FIG.3, upon completion of the desired machining operation,pressure fluid is delivered to the right-hand chamber of the cylinder 40through the fluid passage 45, while removing pressure fluid from theleft-hand chamber through the fluid passage 44. Accordingly, thereciprocating frame work 12 moves toward the left-hand support wall 11"together with the machined work-piece 46 and the die 28. When the die 28comes to a certain position relative to the center holder 29, the valve36 is disabled, so that the center holder 29 moves toward the left-handsupport wall ll" together with the reciprocating frame-work 12, untilthe stopper 35 engages the left-hand support wall 11" when theframe-work 12 comes to rest. In the course of the movement of thereciprocating frame-work 12 toward the left-hand support wall 1 l", theright-hand end of the work-piece 46 leaves the fixed holder member 27and drops, out of the machine tool, as shown by phantom lines in FlG.3.

It is apparent from the foregoing description that, with the machinetool of the present invention, the work-piece is free from excessivestress throughout its extrusion despite its elongation caused by theextrusion, because one end of the workpiece is movably held at aconstant pressure by the auxiliary hydraulic jack including the pressurefluid cylinder connected to the checking constant-pressure valve. Theholding of the two ends of the work-piece at the constant pressurecompletely eliminates the risk of fatigue and breakdown of the workpiecematerial due to repeated vibration, which fatigue and breakdown havebeen experienced with conventional machine tool for similar work.Besides, with the construction of the present invention, there is nodanger of cracking in the proximity of the center holes and metalcreeping" at the ends of machined portions of the work-piece. Thus,shaped products I of high quality can be obtained at high dimensionalaccuracy.

Furthermore, with the machine tool of the present invention, the risk ofadverse bending of the work-piece in the initial stage of machining dueto the presence of unstable regions, which has been troublesome inconventional extrusiontype machining, can completely be eliminated, byholding the work-piece with constant holding pressure by the combinationof the fixed holder member and the movable holder member. By using theholding mechanism of the present invention, the end surface of thework-piece can be formed at right angles to the machined surface, andthe machined surface can be made smoothly regardless of even or unevendistribution of material inthe workpiece of limited degree.

In the machine tool of the invention, the die is floating in alignmentwith the axis of the work-piece by the die holder of the reciprocatingframework 12, so that die travels along the work-piece while keepingexact alignment with the longitudinal axis of the work-piece.Accordingly, extrusion can be effected with reference to the axis of thework-piece, without causing any eccentricity in the unstable region ofthe material and the bending thereof. Thus, axially long work-piece canbe accurately extruded by the machine tool of the present invention,without using any extra guide dies. in addition, a highly accurate axialcenter line is established through the center holes in the finishedproduct, so that such axial center line with the center holes can beadvantageously used in the succeeding lathing and grinding process.Thus, the overall effi ciency of the entire machining process for eachproduct can be greatly improved.

FlGS.4 to 11 illustrate another embodiment of the present 7 Spacingmembers 54, 54, 55, 55', 56, and 56' are secured to the walls 52 and 53at the opposite ends of each spacing member respectively, so as tofirmly hold the two walls 52 and 53 with a fixed spacing. The spacingmembers 54, 54, 55, and 55' are mainly for bearing tensile load, whilethe spacing members 56 and 56' are mainly for bearing compressive load.

A bolster-side or an auxiliary hydraulic jack side die holder 65 and amain ram-side or a main hydraulic jack side die holder 60 are disposedin the space defined between the two support walls 52 and 53. A movableflange 58 is disposed on the side of the right-hand support wall 53.

The bolster-side die holder 65 and the flange 58 are connected togetherby a pair of connector rods 63 and 64- which rods slidingly extendthrough a pair of guide bearings 60' provided on the main ram-side dieholder 60. In the embodiment, as illustrated in FIGSA to 11, theconnector rods 63 and 64 extend through a hollow space of the right-handsupport wall 53 without engaging the latter. The opposing ends of eachconnector rod 63 or 64 are integrally connected to the bolsterside dieholder 65 and the flange 58, respectively, by suitable fastening means,e.g., double nuts.

The flange 58 is directly connected to a main ram cylinder 57, forinstance by threaded engagement, as shown in F164. A main ram 59, whichis connected to FIGA. piston disposed in the cylinder 57, coaxiallyextends through the cylinder 57 from the piston to the outside of thecylinder 57. Accordingly, the main ram 59 extends through the flange58,and the flange 58 is movable relative to the main ram 59 togetherwith the main ram cylinder 57. The main ram cylinder is slidablysupported on a jack base 74. A tapped ring 61 engages threaded outer endof the main ram 59, and ring 61 is secured to the ram-side die holder 60through a pad 62 by threaded bolts 61', as shown in FIG. 4 Thus, themain ram 59 is connected to the ram-side die holder 60. v

A fixed holder member 66 is secured to the central portion of theram-side die holder 60. A movable holder member 71 is connected to anauxiliary ram 69, as will be described hereinafter. The two centers 66and 71 are secured to the machine tool in such a manner that the center66 faces the other center 71 in alignment with each other.

The outer end of the auxiliary ram 69 is connected to one side of acenter guide 70, and the opposite side of the center guide 70 holds themovable holder member 71. The center guide 70 preferably includes alarge diameter portion to facilitate the selective engagement of theguide 70 with a pad 72 secured to the left-hand support wall side of thebolsterside die holder 65.

In the embodiment of P164, the bolster-side die holder 65 and the flange68 integral with the main ram cylinder 57, which are connected togetherwith the connector rods 63 and 64, constitutes a reciprocatingframe-work A movable relative to the leftand right-hand support walls 52and 53 steadfastly fixed to the machine frame 51. The upper portion ofthe ramside die holder 60 provides for the guide bearings 60' guidingthe reciprocation of the frame-work A, and the central portion of theholder 60 is connected to the main ram 59 extending from the main ramcylinder 57 and holds the fixed holder member 66, and the lower portionof the holder 60 simply sits on the smooth top surface 51 of the frame51. A ram-side die 67 is mounted on the ram-side die holder 60 inalignment with the fixed holder member 66. It should be noted here thatalignment is established in the machine tool on the frame 51 among thefixed holder member 66, the ram-side die 67, the movableholder member71, and the bolster-side die 68.

A work-piece 73 to be machined by the machine tool of H044 is pretreatedby forming center holes at its opposing end surfaces, and its diameteris made substantially equivalent to holder member 71, while the oppositeend of the work-piece 73 engages the approach or entry of the ram-sidedie 67 with a spacing from the fixed holder member 66. To establish thecondition of FIG.7, the longitudinal axial center line of the pretreatedwork-piece is held between the die holders 60 and 65 in alingnment withthe fixed holder member 66 and the movable holder member 71, by asuitable holding means (not shown), and the solenoid SOL-l of a solenoidvalve in the hydraulic control system of FIG. is actuated. Theconstruction of the solenoid valve is such that its spool moves to theright, as seen in FIG, upon actuation of the solenoid SOL- 1, so thatpressure fluid from a pump P is delivered to the auxiliary ram cylinder75 through itsfluid inlet passage 69' so as to urge the auxiliary ram 69to the right. At the same time, the

pressure fluid from the pump P is also delivered to the main ramcylinder57 through its fluid passage 57", so as to apply pressure to theright-hand side of the piston of the main ram 59. Since the main ramcylinder 57 is movable while the auxiliary ram cylinder 75 isstationary, the auxiliary ram 69 moves to the right, as seen in FIGSAand 11, to cause. the center guide 70 to engage the pad 72 secured tothe ram-side die holder 65 for moving the reciprocating frame-work A tothe right, so that the flange 58 of the frame-work A travels to theright together with the main ram cylinder 57. During this movement ofthe main ram cylinder 57v the movable holder member 71 secured to theouter end of the auxiliary ram 69 comes into engagement with the centerhole at the left-hand end of the work-piece 73, and asthe auxiliary ram69 further moves rightwards, the right-hand end of the work-piece 73 isforced to engage the approach of the ram-side die 67, as shown in FIG.7.

FIG.8 shows the condition of the machine tool at the end of the secondstage of the machining operation, following the first stage; namely, theright-hand end portion of the workpiece 73 is machined by the ram-side67, and the center hole at the righthand edge surface of the work-piece73 is brought into operative engagement with the fixed holder member 66,so as to hold the work-piece 73 by the two holder members 66 and 71 ofthe machine tool for allowing the removal of the work-piece holdingmeans used in the first stagesThe condition of FIG.8 is established bythe continuation of the rightward stroke of the auxiliary ram 69.

More particularly, when the right-hand end of the workpiece 73 engagesthe approach of the ram-side die 67 as shown in FlG.7, as the pressurefluid is delivered to the main ram cylinder 57, the main ram cylinder 57moves to the right together with the reciprocating frame-work A, untilofthe bolster-side die holder 65 causes the bolster-side die 68 to engagethe left-hand edge of the work-piece 73, because the movement of theauxiliary ram 69 is resisted by the ram-side die 67. After both of theopposite ends of the work-piece 73 are brought into engagement with thedies 67 and 68, respectively, further delivery of the pressure fluid totwo ram cylinders 57 75 will begin the machining operation of theworkpiece 73. In this embodiment, the main ram-side die 67 is selectedto begin the machining before the bolster-side die 68. Thus, in responseto the further application of pressure fluid, the auxiliary ram 69 movesto the right, so as to force the workpiece 73 to the right, so that theright-hand end portion of the work-piece 73 is machined or extruded bythe ram-side die 67, until the center hole formed on the right-hand edgesurface of the work-piece 73 engages the fixed holder member 66. The pad62 secured to the ram-side die holder 60 actsto limit the rightwardmovement of the fixed holder member 66.

It is noted that the extrusion of the ri ght-hand end of the workpiece73 by the main ram-side die 67 tends to generate such adverse strain inthe work-piece 73 as to cause inaccuracy in the extrusion. According tothe present invention, the danger of such adverse strain is completelyeliminated by providing a checking constant-pressure valve CV at theauxiliary ram cylinder 75. When the resistance to the extrusion of thework-piece 73 causes the fluid pressure to rise in excess of a certainpredetermined level, the valve CV acts to partially release the fluidpressure from the auxiliary ram cylinder 75, so as to maintain asubstantially constant fluid pressure in the ram cylinder 75 whileallowing the auxiliary ram 69 to move leftwards, as seen in FIGSA and11. Thereby, the work-piece 73 is allowed to elongate, and the holdingpressure at the opposite end of the work-piece 73 is kept substantiallyconstant without causing any adverse strain in the work-piece 73.

In the second stage of the machining operation, it is apparent that thepressure fluid delivered to the main ram cylinder. 57 cannot cause themain ram 59 to move to the left, because the auxiliary rarn cylinder 75having the same fluid pressure as that of the main ram cylinder 57 isheld stationary while the main ram cylinder 57 itself is movable.

FIG.9 shows an intermediate condition of the machine tool during thethird stage of the machining operation, which follows the aforesaidsecond stage. During the third stage, the left-hand side of thework-piece 73 is machined or extruded by the bolster-side die 68, whichis now held by the two holder members 66 and 71. As the pressure fluidis continuously fed to the main ram cylinder 57, the cylinder 57 movesto the right together. with the reciprocating frame-work A, because theauxiliary ram 69 cannot move rightwards due to the limitation by the pad62 on the main ram-side die holder 60. Thereby, the bolster-side die 68carried by the bolster-side die holder 65 of the reciprocatingframe-work A extrudes the left-hand side portion of the work-piece 73,as shown in FIG.9, so as to form liner grooves 73' (FIGS-A) of thework-piece 73 in parallel with the axis defined by the fixed holdermember 66 and the movable holder member 71.

During the extrusion by the bolster-side die 68 in the third stage ofthe machining operation, the work-piece 73 is allowed to elongate by theaction of the checking constant-pressure valve CV. Thereby, the dangerof adverse strain on the workpiece 73 is completely eliminated, and theholding pressure is kept substantially constant for ensuring highlyaccurate machining of the work-piece 73, while maintaining exact axis ona line connecting the fixed holder member 66 and the movable holdermember 71.

When the desired length of the workpiece 73 is machined, the third stageof the machining is completed, for instance by a limit switch (notshown) which de-energize the solenoid SOL-l of the solenoid valve in thehydraulic system of F 10.1 1.

Throughout the second stage (FIG.8) and the third stage (FIG.9) of themachining, even if unbalanced strain is caused in unstable regions ofthe work-piece 73 by the die 67 or 68, the constant holding pressure atthe two holder members 66 and 71 prevents the work-piece 73 fromdeviating from the axis defined by the two holder members 66 and 71,which engages preformed center holes of the work-piece 73, respectively.

It should be noted here that the ram-side die holder 60 and bolster-sidedie holder 65 are both slideably disposed on the machine frame 51, sothat each of the two holders 60 and 65 can move on the machine frame 51to a limited extent. For instance, in the case of slight flexing of thework-piece 73, either holder 60 or 65 can move slightly in parallel withthe axial center line of the work-piece 73, as defined by the fixedholder member 66 and the movable holder member 71, so that effectiveextrusion by the die 67 or 68 can be ensured.

FIG.10 shows an intermediate condition of the machine tool during thefourth stage of machining operation. When the end of the third stage isdetected, e.g., by the aforesaid limit switch, another solenoid SOL-2 ofthe solenoid valve in the hydraulic control system of FIG. 1 1 isenergized. Accordingly, the right-hand end of the valve spool isconnected to the hydraulic system, so that the pressure fluid is drainedfrom the auxiliary ram cylinder 75, through the opening 69' and from theright-hand chamber of the main ram cylinder 57 through the fluid passage57 while delivering the pressure fluid to the left-hand side chamber ofthe main ram cylinder 57 at the lefihand side of the piston through thepassage 57'. Thus, the main ram cylinder 57 moves leftwards togetherwith the reciprocating frame-work A, while forcing the auxiliary ram 69to the left, as shown in FIGJO. In the beginning of this left wardmovement of the reciprocating frame-work A, the ramside die holder 60tends to move together with the work-piece 73, but due to the inertia ofthe holder 60 and the main ram 59 connected thereto and the relatedfriction, the ram-side die holder 60 remains stationary and thework-piece 73 leaves the ram-side die 67 carried by the holder 60. Thereaction of the leftward movement of the main ram cylinder 57 istransmitted to the main ram 59, so as to urge the ram-side die holder 60against the stationary right-hand support wall 53 secured to the machineframe 51 for facilitating the separation of the work-piece 73 from theram-side die 67 carried by the holder 60. The bolster side die 68 movesleftwards together with the work-piece 73.

When the flange portion 70 of the center guide 70 carrying the movablecenter 71 engages a strap 52". mounted on the left-hand first supportwall 52, the auxiliary ram 69 comes to rest together with the movableholder member 71 and the workpiece 73, but the bolster-side die holder65 continues its leftward movement. As the right-hand edge of thebolster-side die 68 on the bolster-side die holder 65 passes theleft-hand edge of the work-piece 73, the movablerholder member 71 knocksout the work-piece 73 for removal from the machine tool by a suitablemeans. When the bolster-side die holder 65 returns to its extreme leftposition, or its initial position as shown in FIG.4, the solenoid SOL-2is de-energized by a suitable means (not shown) and one machining cycleis completed, and the machine tool becomes ready for a nexts machiningoperation.

As described in the detailed disclosure of the construction andoperation of the machine tool of the invention, the machine tool canaccurately extrude a work-piece having preformed center holes intodesired shape, such as a splined shaft, a cylindrical gear, a flutedroller, or the like, because the elongation of the work-piece caused bythe extrusion is automatically absorbed by the auxiliary ram 69 providedwith a checking constant-pressure valve CV while maintaining a constantholding pressure. The extrusion of the work-piece 73 in parallel withits longitudinal axis, is defined across the holder members, 66 and 71,by means of the dies 67 and 68 carried by the holders 60 and 65 ensuresaccurate machining of the long work-piece with a well establishedconcentricity, and such extrusion eliminates the need of extra guidedies which have been required in conventionalmachine tool for similarpurposes. Furthermore, the constant holding pressure of the work-pieceby the fixed holder member and the movable holder member completelyeliminates the danger of flexing of the work-piece at its unstableregions and the metal creepage at its end portions, Thus, the need ofproviding extra metal at end portions of the work piece before machiningand the removal of such extra metal after the machining is entirelyeliminated, so that the manhours necessary for such machining cangreatly be reduced. Since the center holes of the work-piece are notaffected by the machining with the machine tool of the invention whilemaintaining an accurate axis therethrough, such center holes can be usedin succeeding finishing treatment of the work-piece, such as finishingby lathing and grinding. Thus, the laborious centering of the toothedwork-piece for the finishing operation and the accompanying boring ofthe center holes become unnecessary, so that the ecomonomy of thematerial is greatly improved while simplifying the finishing process.Consequently, with the machine tool of the present invention, themachining and extruding operation can be remarkably simplified, ascompared with conventional machine tools.

If the machine tool of the present invention is provided with a suitablework-piece feeder and a work-piece remover, it can be used for massproduction with further saving in the manhours.

Although the present invention has been described with a certain degreeof particularity, it is understood that the present disclosure has beenmade only by way of example and that numerous changes in details ofconstruction and the combination and arrangement of parts may beresorted to without departing from the spirit and the scope of theinvention as hereinafter claimed.

What I claim is:

1. Machine tool for working an extendedly long work-piece such as asteel bar into 'a splined shaft, fluted rod, axially thick pinion or thelike by means of a die adapted to be axially moved relative to saidwork-piece, comprising a machine frame, a first hydraulic jack mountedat one end of said machine frame, a frame-work adapted to bereciprocatingly movable along on said machineframe by means of saidfirst hydraulic jack, said frame-work being provided with the die at theinner end thereof, a fixed holder member having a center pin to engagewith a center hole formed in one end of the work-piece, a movable holdermember having a center pin to engage with the opposite center hole ofthe work-piece, a second hydraulic jack mounted at the other end of saidmachine frame and having a piston connected to said movable holdermember, a source of fluid under pressure, and conduit means forconnecting said fluid pressure source with said first hydraulic jack andthrough a check valve with second hydraulic jack, whereby when saidfirst hydraulic jack is actuated so as to move said frame-work in onedirection,said die may be forcedly pulled along on the work-piece toshape said workpiece while compensating for elongation caused by saidshaping by means of elasticity of the second hydraulic jack, whichelasticity may be controlled by said check valve.

2. Machine tool as set forth in claim 1, in which said machine frame isprovided with two support members on the opposite ends thereof and saidreciprocatingly movable framework comprises two end members and at leastone pair of parallel beams for connecting said end members together, oneof said support members of the machine frame having bearing forjournalling said beams of the frame-work for longitudinal movement ineither direction thereof and being fixedly provided with said holdermember with the center pin and further a cylinder of said firsthydraulic jack of which piston is connected via its piston rod with oneof said end members of the frame-work so as to be moved in eitherdirection depending on which chamber of the cylinder the fluid underpressure is supplied, the other support member of the machine framebeing provided with a cylinder of said second hydraulic jack so as toextend its piston rod toward said fixed holder member with the centerpin, the free end of said piston rod having the movable holder memberwith its center pin so as to elastically hold the work-piece togetherwith said fixed center pin therebetween, the other end member of theframe-work being mounted with the die so as to allow the movable holderand the work piece engaged therewith to pass through said die.

3. Machine tool as set forth in claim 1, in which said machine frame isprovided with two support members on the opposite ends thereof and saidreciprocatingly movable framework comprises two end members and at leastone pair of parallel beams for connecting said end members together, oneof said support members of the machine frame having bearings forjournalling said beams of the frame-work for longitudinal movement ineither direction thereof and having said holder member with its centerpin fixed therewith and further having a piston rod of said firsthydraulic jack of which cylinder is fixed to the outer side of said oneend member of the frame-work so as to be moved in either directiondepending on which chamber of the cylinder the fluid under pressure issupplied, the other support member of the machine frame being providedwith a cylinder of said second hydraulic jack so as extend its pistonrod toward said fixed holder member with the center pin for elasticallyholding the work-piece together with said fixed center pin therebetween,the other end member of the frame-work being mounted with the die so asto allow the movable holder and the work-piece engaged therewith to passthrough said die.

4. Machine tool as set forth in claim 3, which further comprises asecond die mounted at said one support member in alignment with thefirst die and the two center pins so that the work-piece held by themovable center pin atone end and by an enlarged mouth of said second dieat the other end may be worked first until said other end of thework-pieceabuts on the fixed center pin by means of said second die, andsecond, with the work piece now held between the two center pins, workedat the other end by means of said first die.

1! t i l

1. Machine tool for working an extendedly long work-piece such as asteel bar into a splined shaft, fluted rod, axially thick pinion or thelike by means of a die adapted to be axially moved relative to saidwork-piece, comprising a machine frame, a first hydraulic jack mountedat one end of said machine frame, a framework adapted to bereciprocatingly movable along on said machine frame by means of saidfirst hydraulic jack, said frame-work being provided with the die at theinner end tHereof, a fixed holder member having a center pin to engagewith a center hole formed in one end of the work-piece, a movable holdermember having a center pin to engage with the opposite center hole ofthe work-piece, a second hydraulic jack mounted at the other end of saidmachine frame and having a piston connected to said movable holdermember, a source of fluid under pressure, and conduit means forconnecting said fluid pressure source with said first hydraulic jack andthrough a check valve with second hydraulic jack, whereby when saidfirst hydraulic jack is actuated so as to move said frame-work in onedirection,said die may be forcedly pulled along on the work-piece toshape said work-piece while compensating for elongation caused by saidshaping by means of elasticity of the second hydraulic jack, whichelasticity may be controlled by said check valve.
 2. Machine tool as setforth in claim 1, in which said machine frame is provided with twosupport members on the opposite ends thereof and said reciprocatinglymovable frame-work comprises two end members and at least one pair ofparallel beams for connecting said end members together, one of saidsupport members of the machine frame having bearing for journalling saidbeams of the frame-work for longitudinal movement in either directionthereof and being fixedly provided with said holder member with thecenter pin and further a cylinder of said first hydraulic jack of whichpiston is connected via its piston rod with one of said end members ofthe frame-work so as to be moved in either direction depending on whichchamber of the cylinder the fluid under pressure is supplied, the othersupport member of the machine frame being provided with a cylinder ofsaid second hydraulic jack so as to extend its piston rod toward saidfixed holder member with the center pin, the free end of said piston rodhaving the movable holder member with its center pin so as toelastically hold the work-piece together with said fixed center pintherebetween, the other end member of the frame-work being mounted withthe die so as to allow the movable holder and the work piece engagedtherewith to pass through said die.
 3. Machine tool as set forth inclaim 1, in which said machine frame is provided with two supportmembers on the opposite ends thereof and said reciprocatingly movableframe-work comprises two end members and at least one pair of parallelbeams for connecting said end members together, one of said supportmembers of the machine frame having bearings for journalling said beamsof the frame-work for longitudinal movement in either direction thereofand having said holder member with its center pin fixed therewith andfurther having a piston rod of said first hydraulic jack of whichcylinder is fixed to the outer side of said one end member of theframe-work so as to be moved in either direction depending on whichchamber of the cylinder the fluid under pressure is supplied, the othersupport member of the machine frame being provided with a cylinder ofsaid second hydraulic jack so as extend its piston rod toward said fixedholder member with the center pin for elastically holding the work-piecetogether with said fixed center pin therebetween, the other end memberof the frame-work being mounted with the die so as to allow the movableholder and the work-piece engaged therewith to pass through said die. 4.Machine tool as set forth in claim 3, which further comprises a seconddie mounted at said one support member in alignment with the first dieand the two center pins so that the work-piece held by the movablecenter pin at one end and by an enlarged mouth of said second die at theother end may be worked first until said other end of the work-pieceabuts on the fixed center pin by means of said second die, and second,with the work piece now held between the two center pins, worked at theother end by means of said first die.